Entities with substantial printing demands typically use a production printer. A production printer is a high-speed printer used for volume printing, such as a continuous-forms printer that prints on a web of print media stored on a large roll. A production printer typically includes a localized print controller that manages the overall operation of the printing system, and a marking engine (sometimes referred to as an “imaging engine” or a “print engine”). The marking engine includes one or more arrays of printheads.
Upon receiving a print job, the print controller rasterizes logical pages of the job (e.g., to create bitmaps representing each page of the job), and the marking engine operates individual printheads to mark the web based on the rasterized logical pages. Thus, the printer marks physical pages based on the digital information of the print job.
A Print Verification System (PVS) verifies that the physical output of a printer is error-free. Thus, a PVS may scan the printed pages of a job from a production printer, and may compare each printed page to a corresponding rasterized version kept in memory. If there is a discrepancy, such as an errant droplet of ink, the PVS may identify the error and report it for handling by an operator of the printer.
While a PVS is useful for detecting errors in a printed job, a PVS may encounter substantial problems when attempting to review output from a production printer that utilizes parallel processing. For example, some printers include multiple Raster Image Processors (RIPs), and send out batches of pages (one to each RIP) for rasterization by the RIPs. As pages are rasterized by the RIPs, they are sent out to the PVS in their order of completion. This means that while the physical pages of a print job may be received in order at the PVS, the rasterized pages may be received out of order. This situation makes it harder for a PVS to determine which physical page of the job each rasterized page corresponds with, which may result in substantial processing delays.